1. Field of the Invention
The present invention relates to a memory device and a method for accessing the memory device thereof, more particularly, to a memory device with high securing function and the accessing method thereof.
2. Description of the Prior Arts
Data, software, computer program or high confidential information stored in the non-volatile memory, for example, read-only memory (ROM), may be stolen easily by some kinds of method. The method usually is so called “Chip De-cap” or “Dump ROM Code”. The technology of Chip De-cap comprises removing the package of chip and probing the particular data pins for the data information stored in the memory. The technology of Dump ROM Code comprises issuing an instruction to retrieve binary code via I/O ports and reversing binary code to assembly code by a revering program. Therefore, if the data/address stored in the ROM memory are not encoded, they are easily stolen by the above means.
U.S. Pat. No. 7,171,566 B2 discloses a computer processing apparatus, when writing data to, and/or reading data from, memory, one or more instruction bits are associated with the memory address for the data to specify how encryption or decryption is to be performed. However, the address itself suggested in 566′ does not be encoded, let alone for serving the purpose of preventing the technique of Chip De-Cap or Dump ROM Code.
U.S. Publication No. 2007/0061595 discloses an apparatus and a method for protecting data. The apparatus includes a sequential-key comparator and a scrambling device. However, the scrambling device is not for encoding for serving the purpose of preventing the technique of Chip De-Cap or Dump ROM Code. More particularly, the data/address stored in the storage device 250 is not encoded by software, so the data stored in the 250 can be found by De-cap.
Accordingly, in view of the above drawbacks, it is an imperative that a ROM device for practicing secret is designed so as to solve the drawbacks as the foregoing.